Micro-gyroscope and method for operating a micro-gyroscope

ABSTRACT

A micro-gyroscope for determining a rate of rotation about a Z-axis includes a substrate and two sensor devices each of which comprises at least one drive mass, at least one anchor, drive elements, at least one sensor mass and sensor elements. The drive mass is mounted linearly displaceably in the direction of an X-axis, and can be driven in an oscillatory manner with respect to the X-axis. The sensor mass is coupled to the drive mass by means of springs. The sensor mass is displaceable in the Y-direction, and sensor elements detects a deflection of the sensor mass in the Y-axis. The two sensor devices are disposed parallel to each other and one above the other in the direction of the Z-axis, and the drive mass in these two sensor devices are coupled to each other by means of a coupling spring.

CROSS REFERENCE TO RELATED APPLICATIONS

The application claims the benefit of German Application Serial No. 102011 057 032.2, entitled “Mikro-Gyroskop and Verfahren zum Betreibeneines Mikro-Gyroskops”, filed on Dec. 23, 2011, the subject matter ofwhich is incorporated herein by reference.

BACKGROUND

A. Technical Field

The present invention relates to a micro-gyroscope for determining therate of rotation about a Z-axis, having a substrate and having a firstand second sensor device, wherein each sensor device comprises at leastone drive mass disposed parallel to the substrate and at least oneanchor by means of which the drive mass is attached to the substrate. Atleast one anchor spring is disposed between the anchor and the drivemass so that the drive mass is mounted linearly displaceably in thedirection of an X-axis, and rigidly in the direction of a Y-axis and aZ-axis. Drive elements by means of which the drive mass can be driven inan oscillatory manner in the direction of the X-axis, at least onesensor mass connected to the drive mass by means of springs such thatsaid sensor mass is connected to the drive mass rigidly in theX-direction and Z-direction and displaceably in the Y-direction, andsensor elements for detecting a deflection of the sensor mass in thedirection of the Y-axis are also present.

B. Background of the Invention

Generic micro-gyroscopes are known, wherein a plurality of identicalsensor devices are disposed adjacent to each other, and the drive massesthereof are coupled to each other. Reliable data capture relative tojust one sensor device is thereby provided, because as a rule aplurality of sensor masses are present and are deflected when a rate ofrotation occurs. By comparing the measured values of the two sensormasses, a conclusion can be drawn about the correctness of themeasurement signals obtained. A disadvantage of said type ofmicro-gyroscope is the large installation space required for the twosensor devices disposed adjacent to each other on the substrate.

SUMMARY OF THE INVENTION

The object of the present invention is thus to provide micro-gyroscopesthat function reliably and are able to provide redundant measurementresults, allowing conclusions about the correctness of the measurementto be drawn, and additionally requiring only a small installation space.

The object is achieved by a micro-gyroscope having the characteristicsof claim 1 and by a corresponding method for operating amicro-gyroscope.

The micro-gyroscope according to the invention for determining the rateof rotation about a Z-axis comprises a substrate and a first and asecond sensor device. Each sensor device has at least one drive massdisposed parallel to the substrate and at least one anchor by means ofwhich the drive mass is attached to the substrate. The drive mass ismounted linearly displaceably in the direction of an X-axis, and rigidlyin the direction of a Y-axis and a Z-axis, by means of at least oneanchor spring disposed between the anchor and the drive mass.

Drive elements by means of which the drive mass can be driven in anoscillatory manner in the direction of the X-axis and at least onesensor mass connected to the drive mass by means of springs such thatsaid sensor mass is connected to the drive mass rigidly in theX-direction and Z-direction and displaceably in the Y-direction are alsopresent. A deflection of the sensor mass in the direction of the Y-axisis detected by sensor elements.

According to the invention, the two sensor devices are disposed parallelto each other and one above the other in the direction of the Z-axis.The drive masses of the first and the second sensor device, referred tobelow as the first and second drive masses, are connected to each otherby means of a coupling spring. By synchronously driving the drive massesof the two sensor devices, when a rate of rotation occurs, synchronousdeflection of the sensor masses of the two sensor elements is alsoexpected. The sensor elements associated with each sensor mass thusoutput identical signals. If the signals do not match, then it can beconcluded that, for example, damage has occurred to the sensor or animpact has been made on the sensor. The received signals must thereuponbe corrected or discarded.

A substantial advantage of the present invention is that the sensormasses are deflected within the X-Y plane in which the drive mass isalso disposed. Installation space outside of the X-Y plane is notrequired for this sensor. In addition to the small area required by themicro-gyroscope according to the invention on the substrate, a very lowinstallation height is hereby made possible by the micro-gyroscope. Thetwo planes in which the first and second sensor device are disposed canbe very close to each other, because no components are displaced out ofsaid plane. The sensor according to the invention is thus very compactin construction, but still reliable with respect to the measurementsthereby produced.

The first and second drive mass are preferably attached to the sameanchors on the substrate. A compact design is also possible because thedrive masses of the first and second sensor device use at leastpartially the same mountings. One anchor thus extends over a pluralityof planes in the Z-direction, so to speak. The anchor is attached at oneend to the substrate and allows the individual drive masses of thesensor device to be disposed at different distances from the substrate.Of course, however, each sensor device can have a dedicated mounting andanchor.

In an advantageous embodiment of the invention, the sensor elements areelectrode pairs, wherein one electrode is connected to the substrate ina stationary manner, and the other electrode is disposed on the sensormass that can be displaced in the direction of the Y-axis. Thestationary electrodes can thereby be stationary and disposed between thesubstrate and the first sensor device, between the first and secondsensor device, and/or between the second sensor device and a furtherlayer disposed above the second sensor device, such as a cover of themicro-gyroscope.

It is particularly advantageous, when the drive masses are operated inantiphase to each other, if the electrode pairs of the first sensordevice have the opposite polarity of the electrode pairs of the secondsensor device. After the two sensor mass are deflected in oppositedirections to each other in case of an opposite displacement of thedrive masses when a Z rate of rotation occurs, it is advantageous ifeach of the electrode pairs also has the opposite polarity. This resultsin comparable signals that largely correspond to each other, in order toindicate a correct deflection of the sensor masses.

In order to obtain a further improvement of the micro-gyroscopeaccording to the invention, further sensor devices can also beassociated with the first and second sensor devices. It is thereforeadvantageously possible that the micro-gyroscope comprises a third andfourth sensor device, implemented identically to the first and secondsensor device. Said third and fourth sensor devices can either bedisposed above the first and second sensor device again, so that notonly two planes, but a plurality of planes of sensor devices arepresent. It is particularly advantageous, however, if the third andfourth sensor device are disposed in the planes of the first and secondsensor device. The required area for the sensor device on the substrateis indeed thereby increased, but the capture of the signals and drivingof the drive masses is thereby simplified.

Either additional rates of rotation can be captured by the furthersensor devices, or, particularly advantageously, a further verificationof the sensor signal and additional robustness of the sensor can beobtained. This is particularly the case if the first and second sensordevice are connected to the third and fourth sensor device by means of acoupling spring. The drive masses disposed adjacent to each other in oneplane thus oscillate either identically or in opposition, and the drivemasses disposed diagonally to each other can be driven to oscillateeither identically or in opposition, that is, in phase or in antiphase.A plurality of sensor signals is thereby obtained that can be comparedto each other or differentiated, whereby the accuracy of themicro-gyroscope is significantly increased.

In a method according to the invention for operating a micro-gyroscopeaccording to one or more of the features of the previously describedmicro-gyroscope, a rate of rotation about a Z-axis is determined.According to the invention, the drive masses disposed one above theother and having the drive elements are driven to oscillate inantiphase. When the substrate is rotated about a Z-axis, the sensormasses are then deflected in antiphase oscillation in the plane of theassociated drive mass by a Coriolis force. The operation of themicro-gyroscope in antiphase is particularly stable and largely free ofinternal interference. A very clear sensor signal is thereby obtained.

It is also advantageous if, with four sensor devices, the drive massesand sensor masses disposed adjacent to each other one a plane aredisplaced in antiphase. Said mode of operation also ensures a veryreliable sensor signal.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages of the invention are described in the followingexemplary embodiments. There is showing:

FIG. 1 a sketch of a plan view of a first sensor device,

FIG. 2 the plan view of a sketch of a second sensor device,

FIG. 3 a sketch of a section through the first and second sensor deviceof FIG. 1 and FIG. 2,

FIG. 4 a sketch of a plan view of a further sensor device,

FIG. 5 a cross section through FIG. 4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a sketch of a plan view of a first sensor device 1. Thefirst sensor device 1 comprises a frame-shaped drive mass 1.2 that isattached to an anchor 40 by means of anchor springs 1.3. The anchor 40,in turn, is attached to a substrate (not shown) below the drive mass1.2. The drive mass 1.2 is driven to oscillate in the X-direction bymeans of drive elements (not shown), such as comb electrodes. A sensormass 1.5 is disposed in the interior of the frame of the drive mass 1.2.The sensor mass 1.5 is connected to the drive mass 1.2 by means ofsprings 1.6.

While the anchor springs 1.3 allow displaceability of the drive mass 1.2in the X-direction, but said mass is rigidly constructed in theY-direction and Z-direction, the spring 1.6 is designed such that itdoes indeed move the sensor mass 1.5 together with the drive mass 1.2 inthe X-direction, but allows the sensor mass 1.5 to be deflected in theY-direction when a Coriolis force occurs. The spring 1.6 is also stiffin the Z-direction, so that the sensor mass 1.5 is displaceable onlywithin the X-Y plane.

In order to capture the displacement of the sensor mass 1.5 in theY-direction, sensor electrodes 1.7 and 1.8 are provided. The sensorelectrodes 1.7 and 1.8 have opposite polarity, wherein the sensorelectrode 1.7 has a positive and the sensor electrode 1.8 has a negativecharge, for example. The distance of the sensor mass 1.5 from thecorresponding electrode changes due to the displacement of the sensormass 1.5 in the Y-direction, whereby a signal change is generated. Aftersaid signal change, a conclusion is drawn about a Z rate of rotation,that is, the micro-gyroscope or the substrate on which the anchors 40are mounted has been rotated about the Z-axis.

A coupling spring 1.9 and a connection 10 are disposed on the drive mass1.2. The first sensor device 1 of FIG. 1 is connected to the secondsensor device 2 of FIG. 2 by means of the coupling spring 1.9 and theconnection 10, which is provided on both sides of the drive mass 1.2.The connection 10, in particular, connects the coupling spring 1.9 tothe coupling spring 2.9. The coupling spring 2.9, in turn, is connectedto the frame of the drive mass 2.2 of the second sensor device 2. Thedrive mass 2.2 is also attached to four anchor springs 2.3, bringingabout a mounting of the drive mass 2.2 on the anchors 40.

The second sensor device 2 is disposed in a second plane parallel to thefirst sensor device 1 and parallel to the substrate. It is constructedjust like the first sensor device 1. It also comprises a sensor mass 2.5in the interior of the frame of the drive mass 2.2. that can bedeflected in the Y-direction as soon as a Coriolis force occurs due to arate of rotation about the Z-axis. The sensor electrodes 2.7 and 2.8associated with the sensor mass 2.5, in contrast, have polarity oppositeto that of the sensor electrodes 1.7 and 1.8 of the first sensor device1. Accordingly, the sensor electrodes 2.7 have negative and the sensorelectrodes 2.8 have positive polarity. This ensures that when the twodrive masses 1.2 and 2.2 are operating in antiphase, the sensor masses1.5 and 2.5 are also deflected in antiphase, and a correspondinglycorrect signal can be output to the analysis device. It alsoalternatively possible that the sensor electrodes have the samepolarity. A corresponding analysis in the analysis electronics can alsocorrectly process said signals.

FIG. 3 shows a cross section through the two sensor devices 1 and 2. Thearrows P indicate the antiphase displacement of the drive masses 1.2 and2.2. The drive masses 1.2 and 2.2 move back and forth in theX-direction. Said masses are connected to each other by means of thecoupling springs 1.9 and 2.9 and the connection 10. The coupling springs1.9 and 2.9 are alternately extended and compressed, while theconnections 10 remain at rest for in-phase oscillation of the drivemasses 1.2 and 2.2.

A further exemplary embodiment of the present invention is shown in FIG.4. The plan view of the sketch shows that two sensor devices 1 and 3 aredisposed adjacent to each other in an X-Y plane. The two sensor devices1 and 3, in turn, are implemented identically. Said devices comprise adrive mass 1.2 and 3.2, a sensor mass 2.5 and 3.5 being disposed in theframes thereof. The springs 1.6 and 3.6 allow a displacement of thesensor mass 1.5 and 3.5 in the Y-direction.

The drive masses 1.2 and 3.2 are attached to the anchors 40 in theX-direction by means of the anchor springs 1.3 and 3.3. The sensorelectrodes 1.7 and 1.8, and 3.7 and 3.8, have opposite polarity, thatis, sensor electrode 1.7 has positive and sensor electrode 3.7 hasnegative polarity, while sensor electrode 1.8 has negative and sensorelectrode 3.8 has positive polarity. An antiphase deflection of thesensor masses 1.5 and 3.5 corresponding to the antiphase displacement ofthe drive masses 1.2 and 3.2 is thereby correctly captured.

The first sensor device 1 also has coupling springs 1.9, just as in theexemplary embodiment of FIG. 1. The third sensor device 3correspondingly comprises coupling springs 3.9. The coupling springs 1.9and 3.9 disposed between the two drive masses 1.2 and 3.2 are disposedone atop the other, and share a connection 10. The two sensor devices 1and 3 are driven to oscillate synchronously in antiphase by means ofdrive means (not shown.)

A cross section through the exemplary embodiment of FIG. 4 is shown inFIG. 5. It is evident hereby that the drive masses 1.2 and 3.2 aredriven in antiphase to each other. The applies to the sensor devices 2and 4 disposed thereunder. The arrows P also indicate that the sensordevices 1 and 4, and 2 and 3, disposed diagonally from each other, areeach operated synchronously to each other in phase. The two planeshaving the first and third sensor device 1 and 3, and the second andfourth sensor devices 2 and 4, are connected to each other by means ofconnections 10. Synchronous operation of the two planes relative to eachother is also thereby ensured.

The present invention is not limited to the exemplary embodiments shown.In particular, deviations in the shape of the individual masses orelectrodes, and anchors and springs, are possible at any time and can bemodified to meet individual requirements.

What is claimed is:
 1. A micro-gyroscope for determining a rate ofrotation about a Z-axis, comprising: (1) a substrate, and (2) a firstand a second sensor device, wherein each sensor device furthercomprises: at least one drive mass disposed parallel to the substrate,at least one anchor by means of which the at least one drive mass isattached to the substrate, at least one anchor spring disposed betweenthe at least one anchor and the at least one drive mass, by means ofwhich the at least one drive mass is mounted linearly displaceably inthe direction of an X-axis and rigidly in the directions of a Y-axis anda Z-axis, drive elements by means of which the at least one drive masscan be driven in an oscillatory manner in the direction of the X-axis,at least one sensor mass coupled to the at least one drive mass by meansof springs, such that said at least one sensor mass is coupleddisplaceably in the Y-direction and rigidly in the X-direction andZ-direction to the at least one drive mass, sensor elements fordetecting a deflection of the at least one sensor mass in the directionof the Y-axis, wherein the first and second sensor device are disposedparallel to each other and one above the other in the direction of theZ-axis, and wherein the at least one drive mass in the first and secondsensor device are coupled to each other by means of a coupling spring.2. The micro-gyroscope according to claim 1, wherein the at least onedrive mass in the first and second sensor device are attached to thesame at least one anchor on the substrate.
 3. The micro-gyroscopeaccording to claim 1, wherein the at least one drive mass in each caseis a frame enclosing the at least one sensor mass.
 4. Themicro-gyroscope according to claim 1, wherein the sensor elements areelectrode pairs in which one electrode is connected to the substrate ina stationary manner and the other electrode is disposed on the at leastone sensor mass displaceable in the direction of the Y-axis.
 5. Themicro-gyroscope according to claim 4, wherein the electrode pairs of thefirst sensor device have opposite polarity to the correspondingelectrode pairs of the second sensor device.
 6. The micro-gyroscopeaccording to claim 1, further comprising a third and a fourth sensordevices that are implemented identically to the first and second sensordevices.
 7. The micro-gyroscope according to claim 6, wherein the thirdand the fourth sensor devices are disposed in the same planes as thefirst and second sensor devices.
 8. The micro-gyroscope according toclaim 6, wherein the first and second sensor devices are coupled to thethird and fourth sensor devices by means of a coupling spring.
 9. Amethod for operating a micro-gyroscope to determine a rate of rotationabout a Z-axis, comprising the steps of: arranging on a substrate afirst and a second sensor devices, each sensor device including a drivemass, drive elements, at least one sensor mass, and sensor elements(1.7, 2.7), the drive masses in the first and second sensor devicesbeing disposed one above the other; driving the drive masses in thefirst and second sensor devices to oscillate in antiphase with the driveelements; and deflecting the sensor masses in antiphase oscillation inthe plane of the associated drive mass by a Coriolis force when thesubstrate is rotated about a Z-axis.
 10. The method according to claim9, wherein the micro-gyroscope further comprises a third and a fourthsensor devices that are implemented identically to the first and secondsensor devices, and wherein the adjacent drive masses and sensor massesdisposed in one plane are displaced in antiphase.